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v2.4.0

pREST v2.4.0 — opt-in OpenTelemetry instrumentation with a local SigNoz dev stack, pgvector nearest-neighbor ordering and distance filtering, and a pREST Studio dependency upgrade.

Released: July 26, 2026

GitHub tag · Compare v2.3.0...v2.4.0

v2.4.0 is an observability and vector search release. It adds opt-in OpenTelemetry instrumentation with a local SigNoz dev stack (#1003), pgvector nearest-neighbor ordering (_korder) and distance-threshold filtering (:vecdist) (#1011), and a routine pREST Studio dependency upgrade (#1004).

  • Docker: prest/prest:v2.4.0

  • Go install: go install github.com/prest/prest/v2/cmd/prestd@v2.4.0

No breaking changes and no config migrations. Everything new in this release is opt-in: telemetry defaults to off, and _korder / :vecdist only apply where a client sends them against a vector column.

See Changes since v2.3.0 for the commit list.

Highlights

OpenTelemetry instrumentation + SigNoz dev stack (#1003)

Opt-in OTLP/gRPC push telemetry: HTTP, Postgres, and MCP traces; http.server.* / db.client.operation.duration / db.sql.connection.* metrics; and a slog → OTel logs bridge that still writes to stdout. No new HTTP route is added — there is no /metrics scrape endpoint, so the attack surface is unchanged.

New [otel] config section (PREST_OTEL_* env overrides):

Key
Default
Purpose

enabled

false

Master switch — zero overhead and no outbound connections when off

service_name

prestd

Resource service.name

endpoint

(unset)

OTLP gRPC collector host:port

protocol

grpc

Only grpc for now

sample_ratio

1.0

Trace head sampling, clamped 0.0–1.0

metrics_interval

15s

Metric export period

insecure

false

Disable TLS to collector (local/dev)

db_statement

false

Record SQL text on DB spans (trusted envs only)

Setup fails closed: if the exporter can't be built at startup, pREST logs a warning and keeps serving with telemetry disabled. Graceful shutdown (SIGINT/SIGTERM draining via signal.NotifyContext) ships alongside it so telemetry flushes on exit. A self-contained SigNoz stack lives under dev/signoz/ (make signoz-up / make signoz-down) for local viewing. See Configuring pREST — Observability.

pgvector KNN ordering and distance filtering (#1011)

Two new query-parameter forms for vector-typed columns (requires the pgvector extension), both restricted to a fixed metric whitelist (l2/euclidean, cosine/cos, ip/inner/dot, l1/manhattan) and validated end-to-end:

Parameter
Form
Example
Effect

_korder

<column>:<metric>:<vector>

_korder=embedding:l2:[1,0,0]

Orders by nearest-neighbor distance (KNN); composes with _order as an additional sort term

<column>:vecdist

<metric>:<comparison>:<vector>:<threshold>

embedding:vecdist=l2:lt:[1,0,0]:0.5

Filters rows by distance threshold; comparison is restricted to =, !=, <, <=, >, >=

Malformed metrics, non-numeric vector elements, oversized vectors (>16000 dims, pgvector's own limit), non-scalar comparisons (e.g. like), and dimension mismatches all return 400 rather than reaching the database unsafely. See Parameters — pgvector KNN ordering and distance filtering.

pREST Studio dependency upgrade (#1004)

Routine dependency bump for the embedded Studio UI. Fixes the auth dialog not reflecting saved credentials / "remember me" state on reopen, and avoids building incomplete MCP tool-call requests when argument construction fails. No config or API changes.

Changes since v2.3.0

PR
Summary

#1003

Opt-in OpenTelemetry (push) instrumentation — traces, metrics, slog→OTel log bridge — plus a local SigNoz dev stack

#1004

pREST Studio dependency upgrade; auth-dialog and tool-invocation fixes

#1011

pgvector nearest-neighbor ordering (_korder) and distance-threshold filtering (:vecdist)

Full detail: compare v2.3.0...v2.4.0.

Upgrading from v2.3.0

No configuration changes are required; this is a drop-in update.

  1. Deploy prest/prest:v2.4.0, the matching binary, or go install …@v2.4.0.

  2. Telemetry stays off by default. Set otel.enabled = true (or PREST_OTEL_ENABLED=true) and otel.endpoint only when you have an OTLP/gRPC collector to send to — see Configuring pREST — Observability.

  3. pgvector columns gain _korder and :vecdist automatically; both require the pgvector extension on the target column and are no-ops otherwise.

  4. MCP at /_mcp, Studio at /_studio/, and the multi-adapter registry are unchanged from v2.3.0.

Related

PreviousChanges since v2.4.0 (in v2.4.1/v2.4.2)NextChanges since v2.3.0 (in v2.4.0)

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